The invention relates to soil-working machines and more particularly to power harrows carrying a plurality of rotors, which may be rotated about a bearing, such as a friction-resistant bearing; each rotor has a shaft secured thereto and is provided with a tool- or prong-holder, which holder is rotated about a normally vertical axis. The tools or prongs secured to the tool- or prong-holder extend substantially at right angles into the soil, and are used to break up the soil, particularly with a view of preparing the soil to receive seeds.
This type of harrow has the disadvantage that it is relatively easy for debris or vegetable matter to accumulate near the bearings of the rotatable shafts, at the end of which there are disposed the tool- or prong-holders. In practice, it has been shown that the accumulation of such debris, particularly remnants of tree branches and wheat stalks, for example mixed with soil or sand, act as abrasive particles, so that they damage the bearings, which bearings consequently must be replaced at a relatively substantial cost. Apart from the cost, there is also the risk that some vegetable matter, such as vines and the like, intrude into the mechanism and wrap themselves around the bearing or the shaft. This type of intrusion is very hazardous and may impair the motion of the friction-resistant devices, such as ball bearings or the like, incorporated in the bearings of these machines. These vines or other vegetable debris thus effectively reduce the life of any bearings in which the shaft or the prong- and tool-holders are journalled, which may in turn lead, as a result of damage to these bearings, to leakage of lubricating oil carried by the power harrow, and can in an extremecase result in the fracture of the friction-resistant bearings, such as ball bearings, or the like, as the result of introduction of foreign matter into these bearings.
It is therefore necessary to protect these bearings so that the power harrow can operate without there occurring any risk of damage to these machines.
Certain protective measures are known. It is known, for example, to provide along the length of the power harrow additional protective means, such as V-shaped covers. Although an arrangement of this type generally prevents the accumulation of any debris around the bearings, it nevertheless presents the risk of stones being jammed between the tool- or prong-holder and the cover. A jamming of this type may seriously impair the function of the harrow, so that the tool- or prong-holders may be damaged beyond repair. It is a further disadvantage of the cover protective device described that the mounting of the rotors equipped with such a protecting device is relatively complicated, thus takes a long time, and is therefore burdensome.